Cowbirds lay their eggs in the nests of smaller birds. The fast-developing cowbird chicks hatch first, then push the other baby chicks out of the nest as they hatch. The cowbird is classified as a

Options

A. pathogen
B. parasite
C. mutualist
D. commensal

Answer

To classify the cowbird based on the behavior described in the question, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Behavior of Cowbirds**: Cowbirds lay their eggs in the nests of smaller birds. This behavior is crucial to understanding their classification.

2. **Identify the Interaction Type**: The interaction between the cowbird and the host bird (the smaller bird) is one where the cowbird benefits at the expense of the host bird. This is a key characteristic of parasitism.

3. **Define Parasitism**: Parasitism is a biological interaction where one organism (the parasite) benefits from the relationship while the other organism (the host) is harmed. In this case, the cowbird (the parasite) benefits by having its eggs incubated and cared for by the host bird, while the host bird is harmed as its own chicks are pushed out of the nest.

4. **Differentiate from Other Interactions**:
- **Mutualism**: Both species benefit, which is not the case here.
- **Commensalism**: One species benefits while the other is neither helped nor harmed, which is also not applicable since the host bird is harmed.
- **Pathogen**: This term refers to disease-causing agents, which does not fit the cowbird's behavior.

5. **Conclusion**: Given the above points, the cowbird can be classified as a **parasite**, specifically a **brood parasite** because it lays its eggs in the nests of other birds and relies on them for the care of its young.

### Final Answer:
The cowbird is classified as a **parasite**, specifically a **brood parasite**.

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